The present invention relates to a digital conversion circuit for converting from one form of digital modulation(Pulse Code Modulation) to Pulse Width Modulation. In particular, the invention relates to a digital integrated circuit for the control of switching circuits, and in particular, Class D audio amplifiers. A function of the integrated circuit is to accept a digitally encoded audio signal (in the PCM (Pulse Code Modulation) format) and produce a Pulse Width Modulated (PWM) signal, which is used to control a Class D audio amplifier.
Audio amplifiers are power converters that convert the input DC to a desired output AC signal. This output AC signal is then applied to loudspeakers, which in turn produce the desired sound. In order to obtain a good quality sound reproduction, the audio amplifier is required to have a low total harmonic distortion (THD) of the output AC signal throughout the output power range.
Traditionally, class A,B and AB linear amplifiers have been used as audio amplifiers. Presently, Class D switch-mode amplifiers are increasingly replacing the conventional class A and class B amplifiers because they have the advantages of being more efficient and smaller. Recently, different chips which drive class D audio amplifiers have been released by companies like Tripath Technology, Texas Instruments, and Cirrus Logic in the United States; Philips and STMicroelectronics (partnering with ApogeeDDX) in Europe; and Mitsubishi and Sanyo (partnering with Bang & Olufsen) in Japan. Examples include the Mitsubishi M65817A FP, Crystal CS44210 and Texas Instruments TAS5010 or chips. Class D switch-mode amplifiers include both half-bridge and full-bridge switch-mode converter architectures.